docs(Plugins): Added info about folder separator on windows (#7068)

* Added info about folder separator on windows

see https://stackoverflow.com/a/56084864/4255158 for more context.
There should be info about this in the docs!

* simplified regex (removed unnecessary escape char)

src/content/plugins/normal-module-replacement-plugin.mdx

@@ -17,6 +17,8 @@ new webpack.NormalModuleReplacementPlugin(resourceRegExp, newResource);
 
 Note that the `resourceRegExp` is tested against the request you write in your code, not the resolved resource. For instance, `'./sum'` will be used to test instead of `'./sum.js'` when you have code `import sum from './sum'`.
 
+Also please note that when using Windows, you have to accomodate for the different folder separator symbol. E.g. `/src\/environments\/environment\.ts/` won't work on Windows, you have to use `/src[\\/]environments[\\/]environment\.ts/,` instead.
+
 ## Basic Example
 
 Replace a specific module when building for a [development environment](/guides/production).